This invention relates to circuit arrangement means for exciting audible devices, such as buzzers or warning device.
In known arrangements audible warning devices which usually operate from voltages which are unidirectional and lower than mains supply voltage may be driven from an alternating current mains supply but conventionally the associated electrical and/or electronic circuits tend to be bulky.
An object of the present invention is to provide a novel arrangement which may be designed to have low bulk.
According to the invention, there is provided a circuit arrangement means for exciting an audible device, comprising first and second capacitor means, the effective capacitance of the two means being in series for connection across an alternating current mains supply, said second capacitor means having connected across it a rectifier and also the series combination of an electronic voltage sensitive switch and the operating means of the warning device, the arrangement being such that, in operation, the charge on the second capacitor means is periodically discharged through said operating means.
Preferably the first capacitor means has a smaller capacitance value than that of the second capacitor means and the second capacitor means is of the electrolytic type.